Apparent size and apparent distance are power functions of size (length, area, or volume) and distance respectively. The parameters of this power relation, exponent and scale factor, are sensitive to controlling variables such as visual context (for size) and the boundaries of visual space and its differentiation (for distance). By experimentally manipulating the parameters of size and distance scales, several models of size-distance invariance, as well as a relational account of perceived size, will be tested. The development of space perception will be studied by designing bias-free scaling procedures to measure apparent size and distance for children at several ages.